California earthquakes

M4.1 earthquake 19 km NNE of Mesa, California

A magnitude 4.1 earthquake struck 19 km NNE of Mesa, California on Sun, Jul 20, 1986, 7:46 AM PDT (14:46 UTC), 6 km (4 mi) below the surface.

A larger quake followed: M6.4 The 1986 Chalfant Valley, California Earthquake. This one was a foreshock.

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Map

Where this earthquake was located, with the others nearby. Select one for its page.

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The earthquake

Magnitude: 4.1 (ml), light
Local time: Sun, Jul 20, 1986, 7:46 AM PDT
UTC: 1986-07-20 14:46:07 UTC
Depth: 6.1 km (3.8 mi), shallow
Epicenter: 37.575° N, 118.435° W
Region: California
Tsunami flag: No
Status: Reviewed by a seismologist

Did you feel it?

No one has reported feeling this quake to the USGS.

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 0.2 km horizontally, 0.8 km in depth
Depth from: From location
Station coverage gap: 52°
Stations used: 39

Nearest places

Distance and direction from each place to the epicenter, with its forecast.

Nearby

Within 100 km, magnitude 1.5 and up: at least 202 in the 60 days after this one and 127 in the 30 days before it.

After

The first 60 of at least 202.

Before

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Sources

From the USGS Earthquake Hazards Program and its partner networks, event nc99197 (also filed as ci703456, usp0002w7d). Read Tue, Sep 29, 2026, 4:35 PM UTC.